This paper proposes a novel entropy test to determine whether a MUX PUF is linear or not. Three MUX PUF configurations are considered, namely linear, feed-forward and modified feed-forward. In addition to these, we also consider feed-forward structures like overlap, cascade and separate configurations. The approach is focused on computing the conditional entropy of responses to a set of predefined challenges. The challenge set consists of randomly chosen challenges and their 1-bit neighbors. The entropy is computed across the responses of two 1-bit neighboring challenges. For non-linear MUX PUFs like feed-forward, the method determines the MUX stages which are controlled by internally generated challenge bits as opposed to external challenge bits. This is based on the observation that the conditional entropy for each of these stages is zero. Also, the number of zero conditional entropy values across the MUX stages provide an upper bound on the number of internal arbiters present in the PUF. With the proposed approach, we observe 100% sensitivity and 100% specificity for identifying non-linearity. Furthermore, we show that the proposed approach requires very less number of stable random challenges (about 50) for successfully determining whether a PUF is linear or not for real chips.
|Original language||English (US)|
|Title of host publication||IEEE International Symposium on Circuits and Systems|
|Subtitle of host publication||From Dreams to Innovation, ISCAS 2017 - Conference Proceedings|
|Publisher||Institute of Electrical and Electronics Engineers Inc.|
|State||Published - Sep 25 2017|
|Event||50th IEEE International Symposium on Circuits and Systems, ISCAS 2017 - Baltimore, United States|
Duration: May 28 2017 → May 31 2017
|Name||Proceedings - IEEE International Symposium on Circuits and Systems|
|Other||50th IEEE International Symposium on Circuits and Systems, ISCAS 2017|
|Period||5/28/17 → 5/31/17|
Bibliographical noteFunding Information:
This research has been supported by the National Science Foundation under grant number CNS-1441639 and the semiconductor research corporation under contract number 2014-TS-2560.
- MUX PUF
- conditional entropy
- physical unclonable function